This invention relates to an ignition timing adjustment device for an engine, more particularly such a device which simplifies the construction and assembly of the engine.
In internal combustion engines, it is important that the ignition timing (the point during the crankshaft rotation at which the sparkplug fires) be accurately established in order to insure optimum engine performance. Typically, a rotating member, such as a flywheel or a camshaft sprocket driven by the crankshaft, have alignment marks or holes formed adjacent to their peripheries. A timing plate having an indicator member is fixed in position and the ignition timing may be adjusted by visually observing the indicator member and the alignment marks with a timing light. In the actual adjustment of the timing, the piston displacement in its cylinder is checked using a dial gauge to establish a top dead center (TDC) position. The flywheel or camshaft sprocket is then positioned based upon the measurements obtained using the dial gauge. Next, the position of the timing plate is determined and the timing plate is fixed into place. The ignition distributor is rotated until the correct positional relationship between the timing plate indicator and the alignment marks or holes is obtained.
In the prior art, the use of a dial gauge to determine the piston displacement for the engine ignition timing is time consuming and detracts from productivity during the assembly of the engine. In addition, the position of the timing plate must be determined, thereby further slowing down the assembly operation and lengthening the amount of time required for timing adjustment.